An R-2R type D/A converter that uses an R-2R ladder resistor network is known as one of D/A converters for converting digital input signals into an analog signal (Japanese Examined Patent Publication No. 63-47289, for example).
Referring to FIG. 19, a conventional R-2R type D/A converter 100 includes a resistor network 110 and six switches 200 to 205 corresponding to 6-bit digital input signals D0 to D5. The switches 200 to 205 include transistors 200a to 205a that are coupled between a wire 220 with a high voltage VD level and the resistor network 110, and transistors 200b to 205b that are coupled between the resistor network 110 and a wire 221 with a low voltage GND level, respectively. The transistors 200a to 205a and the transistors 200b to 205b turn on/off complementarily, according to the digital input signals D0 to D5. In an illustrated embodiment, each of the switches 200 to 205 is a CMOS inverter circuit.
The R-2R type D/A converter 100 outputs an analog signal Vo having a voltage value obtained by dividing a voltage difference between the high voltage VD and the low voltage GND by resistors contained in the resistor network 110 and on-resistances of the respective transistors 200a to 205a and 200b to 205b. As illustrated in FIG. 20, for example, the R-2R type D/A converter 100 outputs the analog signal Vo having the voltage value corresponding to a code (decimal number) and setting codes (binary numbers represented by the digital input signals D0 to D5). With regard to the voltage value of the analog signal Vo in FIG. 20, the high voltage VD is 6.4 [V], and the low voltage GND is 0 [V]. Each code is the decimal number corresponding to the set of the binary numbers represented by the digital input signals D0 to D5.